Re: [PATCH v5 20/22] virtio_net: set the default max ring num

在 2022/2/17 下午5:30, Xuan Zhuo 写道:

On Thu, 17 Feb 2022 15:21:26 +0800, Jason Wang [off-list ref] wrote:

quoted

On Wed, Feb 16, 2022 at 3:52 PM Xuan Zhuo [off-list ref] wrote:

quoted

On Wed, 16 Feb 2022 12:14:31 +0800, Jason Wang [off-list ref] wrote:

quoted

On Mon, Feb 14, 2022 at 4:14 PM Xuan Zhuo [off-list ref] wrote:

quoted

Sets the default maximum ring num based on virtio_set_max_ring_num().

The default maximum ring num is 1024.

Having a default value is pretty useful, I see 32K is used by default for IFCVF.

Rethink this, how about having a different default value based on the speed?

Without SPEED_DUPLEX, we use 1024. Otherwise

10g 4096
40g 8192

We can define different default values of tx and rx by the way. This way I can
just use it in the new interface of find_vqs().

without SPEED_DUPLEX:  tx 512 rx 1024

Any reason that TX is smaller than RX?

I've seen some NIC drivers with default tx smaller than rx.

Interesting, do they use combined channels?

One problem I have now is that inside virtnet_probe, init_vqs is before getting
speed/duplex. I'm not sure, can the logic to get speed/duplex be put before
init_vqs? Is there any risk?

Can you help me?

The feature has been negotiated during probe(), so I don't see any risk.

Thanks

Thanks.

quoted

Thanks

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Thanks.

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etc.

(The number are just copied from the 10g/40g default parameter from
other vendors)

Thanks

quoted

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
---
  drivers/net/virtio_net.c | 4 ++++
  1 file changed, 4 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index a4ffd7cdf623..77e61fe0b2ce 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c

@@ -35,6 +35,8 @@ module_param(napi_tx, bool, 0644);
  #define GOOD_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
  #define GOOD_COPY_LEN  128

+#define VIRTNET_DEFAULT_MAX_RING_NUM 1024
+
  #define VIRTNET_RX_PAD (NET_IP_ALIGN + NET_SKB_PAD)

  /* Amount of XDP headroom to prepend to packets for use by xdp_adjust_head */

@@ -3045,6 +3047,8 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
                         ctx[rxq2vq(i)] = true;
         }

+       virtio_set_max_ring_num(vi->vdev, VIRTNET_DEFAULT_MAX_RING_NUM);
+
         ret = virtio_find_vqs_ctx(vi->vdev, total_vqs, vqs, callbacks,
                                   names, ctx, NULL);
         if (ret)
--

2.31.0